Okay, so forgive me if I sound like a total idiot, this is my first time posting on here and I'm not exactly a genius when it comes to computers. I do my best, though.
Anyway,
I just recently updated my firefox portable to the newest version and now it won't save any new bookmarks and I lost my (stumbleupon)toolbar and I can't get it to reinstall.
Try a clean install (in a different folder - you don't want to overwrite your existing one!) and see if that fixes the problem. It usually does.
With regards to the StumbleUpon toolbar: do you see it in your addons list? If not, your Firefox profile got corrupted and the fastest way to clean things up is to use a clean install. If you do, and it just says "Not compatible with Firefox 3.6", the problem is the toolbar.
"The question I would like to know, is the Ultimate Question of Life, the Universe and Everything. All we know about it is that the Answer is Forty-two, which is a little aggravating."
Well, I got on and everything that was wrong seems to have gone back to normal. Just a glitch, I guess. Saves me a lot of grief.